The manufacturing of ophthalmic lenses, in particular of single wear soft contact lenses which are used only once and which are disposed of after use, may be performed in a fully automated manufacturing line with the aid of reusable molds. In order to ensure top quality of the so manufactured contact lenses, the contact lenses are optically inspected in-line in an inspection module of the fully automated manufacturing line for the presence of bubbles, edge defects, flaws or inclusions, etc., which would render the contact lenses unacceptable.
During set-up of the manufacturing line, for example before starting a new production lot, new molds are installed on them manufacturing line. Prior to starting “actual” production of contact lenses which are distributed to customers, a predetermined number of “dummy” contact lenses are produced with each of the newly installed molds in order to verify that the newly installed molds are properly arranged so that contact lenses are produced which have the desired specifications. The “dummy” contact lenses are inspected offline to make sure that the contact lenses manufactured with the newly installed molds have the desired specifications including center thickness of the contact lenses. Offline determination of the center thickness of the “dummy” contact lenses may be performed, for example, with the aid of an interferometer. After inspection, the “dummy” lenses are disposed of. Due to the large number of individual molds being present in the manufacturing line, several hundred of “dummy” contact lenses up to a few thousand of “dummy” contact lenses end up as waste even if they fulfill the desired specifications. More importantly, however, the time needed for producing and inspecting the predetermined number of “dummy” lenses prior to starting “actual” production of contact lenses which are distributed to customers may be up to a few hours during which no contact lenses are produced in the manufacturing line that are later on distributed to customers. It goes without saying that this negatively affects the efficiency of the manufacturing line. In addition, for maintaining top quality of the lenses distributed to the customers during “actual” production it is necessary to take samples of lenses out of the “actual” production process at predetermined time intervals in order to make sure that the lenses manufactured during “actual” production have desired specifications.
Therefore, it is an object of the invention to overcome the afore-mentioned disadvantages of the prior art and to suggest a method that greatly increases the efficiency of the manufacturing line during set-up, such as for example before starting a new production lot.